The present invention relates generally to new and improved electrical filter contacts of a type providing protection from broad spectrum electromagnetic interference (EMI) including electromagnetic pulses (EMP). More particularly, the invention is directed to an energy level and frequency discriminating electrical filter contact of a modularized design for selectively providing transient voltage and current overload protection and a filtering of undesired frequency components. The filter contact may be of a miniaturized configuration and is in any event constructed to afford a substantially mechanically stress-free interconnection in the electrical system operating environment.
It has become a common and preferred practice in recent years to incorporate within electrical connectors components for affording a filtering of EMI signals falling outside of a desired signal frequency range or exceeding a given power level, i.e., voltage and current amplitude. The prior art has also contemplated incorporation of current limiting protection in a connector through the provision of suitable DC resistance as well as protection against unwanted voltage transients by use of known electrical breakdown devices. For example, U.S. Pat. No. 3,842,374--Schlicke illustrates several forms of an electrical feedthrough connector providing capacitive filtering of unwanted high frequency interference and surge voltage protection by use of a metal oxide varistor (MOV) which exhibits a low resistance-bypass characteristic in the presence of electrical signals exceeding a predetermined peak voltage value.
U.S. Pat. No. 3,579,155--Tuchto, assigned to the same assignee as the present invention, discloses a filter pin connector including inductive and capacitive reactance components concentrically disposed about a central conductive rod in an appropriate fashion to provide a preselected filtering characteristic. The aforesaid Tuchto patent also discloses the use of flexible conductive bushings or grommets for enabling stress-free interconnection of the contact and the filtering components disposed along the central portion of the contact.
While the prior art and most notably the above described Tuchto patent displays certain advantageous features, none of the prior art provides a full range of EMI protection. Moreover, the prior art does not disclose a contact design that is peculiarly suited for incorporation of selected ones or all of the EMI protection features into a single filter contact by a modularized building block design that facilitates efficient and economical manufacture of such contacts.